Gears of War 3 Game Guide

Act Two: Chapter 3 – Forced Entry

Move up and mow down the first enemy on the right quickly. The point here is to
not let them sound a horn. There are longshots and Oneshots nearby, but if you
have a longshot from the previous chapter you can post up at the first horn 
(careful not to sound it) and look to the wall across the way. There is a guard
that will not move and one that will. Wait for the moving guard to get near
the other and then shoot the stationary guard with a headshot, hit the active
reload, and then you can just hit the explosive barrels on the right as he runs
near them to take him out. A co-op friend can do this as well, but you can
manage on your own.

Now grab the longshots and Oneshot, which is a giant sniper rifle that will
kill the target no matter where you hit. However, it's just up to you if you
want to use the oneshot or longshot. Move over to see the big gate. There are
two guards on either side of the big horn directly above the gate. You may need
to move up a bit to get a clear sight on both, but careful not to move up too
far. By yourself you will have to hit the one on the right and then hit the 
explosives on the left to hit that guard, but you have to be quick or make sure
the left guard is as far away from the horn and try to hit him directly. On
your own this part is tough and I would recommend reloading the checkpoint if
you sound the alarm because you won't be able to get a collectable if you do.
On co-op you can easily coordinate a dual-strike.

*Being detected*

If you do sound an alarm you will have to face Diggers, Drones, and a baby
Corpser. You will also have to fight out of an ambush for the next fight. You
will also be pinned down by turret fire and need to go up and take a walkway to
reach the side cave.

*End being detected advice*

Successfully avoiding detection opens a side door with a small pack of guards,
and then you can go in and pick up a COG tag among some ammo. You will also
pop up in the corner of the next area and be in less peril.

Assuming you took the side path to the next fight, clear your way out and move 
to clear out the Grubs in the cave. Don't run in until you know it's mostly
clear, and then you can kill the turret gunners and shoot the barrels under
the middle turret placement if you want. Then hop on the turret and mow down
the incoming Diggers from the side door. Grab the ammo crate and run into the
next area and take cover in the side alcove out of the turret's sight. Run up 
to the right of the turret and engage the Grenadiers. Toss a frag or two to 
clear them out and flank the turret nest. Pull the lever on the pole to end the